This invention relates to a rail mounting system for mounting a rail on a rail bearing in the permanent way of a railway or like system. In particular, it relates to such systems for use at switches and crossings.
FIG. 1 shows a conventional rail mounting system used at positions away from switches and crossings. The rail 1 is mounted on the sleeper 3 by means of upstanding shoulders 5 cast or glued into the sleeper on either side of the rail, and clips 7 which are anchored to the shoulders, the toes of the clips bearing down onto the flanges on either side of the rail to hold it onto the sleeper. To improve rail-wheel performance, the bearing surface of the sleeper is inclined (not shown), typically by 1:20 or 1:40.
At switches and crossings, due to the diverging or converging tracks, the positions of the rails relative to each other changes from one rail bearer to the next. Since it is not always practical to provide sleepers with appropriately inclined rail bearing surfaces for each position at switches and crossings, flat bearers are often used in such positions. In order to provide an inclination to the rails, it is known to fasten baseplates cast with the required inclination onto the bearers. FIG. 2 shows a known so-called xe2x80x9cpop-up shoulderxe2x80x9d rail mounting system for use at switches and crossings in which the baseplate 10 is formed with a hole or slot on either side of the inclined surface to allow a centre stem shoulder 12, which is cast or glued into the bearer, to pass through the baseplate. The centre stem shoulder provides an orifice for anchoring the middle arm of an elastic rail e-clip 14, the toe of the clip bearing directly down onto the rail flange 16, and the heel bearing down onto a raised reaction pad 18 formed on the baseplate.
Although such rail mounting systems function very well, the manufacturing tolerances required for the shoulders and baseplates must be relatively tight, since any variation in the relative heights of shoulder and baseplate will affect both the toe and heel of the clip, so resulting in a twofold effect on the force exerted by the clip. Furthermore, the baseplates are required to be considerably longer than the width of the rail they are supporting in order to accommodate the hole or slot either side of the rail for receiving the centre stem shoulder and to provide sufficient area for the raised reaction pad. Besides the expense involved with manufacturing long baseplates, at positions where rails converge, such longer baseplates must be replaced by special baseplates which support both converging rails from a position when the rails are further apart than would be the case if shorter baseplates could be used. Such special baseplates are more expensive to produce, since they must be designed for each particular installation position. It is therefore an object to provide a rail mounting system which is cheaper to manufacture and install at switches and crossings than current rail mounting systems.
According to the invention, there is provided a rail mounting system for mounting a rail to a rail bearing, the mounting system comprising a tapered baseplate for supporting the base flange of a rail on the rail bearing at an inclination thereto, and clamp means for urging the-base flange of the rail onto the baseplate and rail bearing, characterised in that the baseplate is secured to the rail bearing solely by virtue of the compressive force exerted by the clamp means through the base flange of the rail.
By securing the baseplate to the rail bearing solely by virtue of the compressive force exerted by the clamp means through the base flange of the rail, the length of the baseplate need be no longer than the width of the rail it supports. This means that rails can be mounted closer together using single-rail baseplates (xe2x80x98standard baseplatesxe2x80x99) than was possible using the xe2x80x9cpop-up shoulderxe2x80x9d system. This means that fewer special baseplates are required per switch/crossing. Furthermore, because the baseplate is only subject to compressive forces, it may be made of relatively low strength materials.
Suitably, each clamp comprises a clip mounted at a suitable height relative to the rail bearing to bear down onto the base flange of the rail. The clip may be mounted on a shoulder upstanding from the rail bearing, and a baseplate locator may be positioned between the baseplate and shoulder to provide a positive location of the baseplate between shoulders.
By use of a baseplate locator as described, the baseplate may be shorter than the width of the rail and yet remain positively located between shoulders such that it cannot move out of position due to any relative movement between the rail and bearer.
Suitably, the baseplate locator comprises a ring mounted around the shoulder and having a peripheral edge that abuts the end of the baseplate. Preferably, the peripheral edge of the ring has a cam profile to allow adjustment of the location of the baseplate by rotation of the ring.
By providing a degree of adjustment of the position of the baseplate in this manner, the same special baseplate design for supporting two adjacent converging rails can be used at several different positions along the track, even though the distance between the rails will be different at each position. In this way the number of special baseplate designs required for each switch and crossing may be further reduced.